214 Value of Native Gold, é&e. 
Having thus arrived at the value of specimens of Gold 
alloyed with Silver, but unmixed with any earthy or stoney 
particles, upon the supposition that the specific gravity of 
such specimens can be obtained to a moderate degree of 
accuracy, the next step is to determine the amount of ex- 
traneous matter in specimens containing evidently masses 
of quartz, or other analogous material, and the reduction in 
value consequent upon such an admixture. 
In order to arrive at a reasonable amount of accuracy in 
such a calculation, it will be necessary to assume an average 
specific gravity as that of the unmixed native Gold of any 
given district :— 
2 
Sp. Gr. 
No. 7 18181 
» 98) 18253 
» 9. 48231 
» 10 18164 
yy wl 18176 
» 12 18688 
13 18606 
14) LS4it 
8| 146710 
18338°75 Mean Specific Gravity. 
For instance, from the above experiments, it may 
be assumed that the average specific gravity of Mount 
Alexander Gold is 18338°75, or say 18300. If, then, 
this be taken as the starting point, it will be easy to 
calculate the reduction in the specific gravity caused by the 
presence of extraneous matter, on the supposition that the 
specific gravity of such matter be known. Now, as a 
general rule, this matter may be taken to be quartz, or some 
material nearly allied to it. Clay and sand can be removed 
by washing, and need not, therefore, be noticed. The 
stoney particles imbedded in the Gold are of such a character 
